Turbine blade



Feb. 24, 1931. B. v. DENSMORE 7 1,793,468

BA! DENSMORE BY cu. 05, M

ATTORNEY mon center.

7 Patented Feb. 24, 1931 BENJAMIN v. nnnslvronn, or Branna/inertia,rnnlvsyrvnnrn, Assrenon T WESTING- rronsn ELECTRIG &nannraorunrne oonranv, A oonronnrron or rnnnsvnfvaivm.

. iA ppl ication filed May28, 1929.;sria1'1vo. 366,618;

. My invention relates to an elastic fluid turbine, more particularly tothe blading thereof,

and it has for an object to provide an improved construction-of blading.1 V

. .More particularly, my invention relates to turbine blades of the sideentry type in which v the root portions are curved to conform in ageneral Way to the curvature of the blade, for

- turbine the purpose of providing increased strength 19 with minimumspacerequireme'nts, as fully set forth in the copending application ofGoldie Back, Serial No. 219,485,1iled September 14, 1927 patented July2, 1929, No. 1,719,415, and assigned to theVVestinghouse Electric 8:Manufacturing Company. In the construction described in the above-mentioned application, the rotor is formed like a disc with transverse,serrated retaining grooves or slots of curved form and the rootsoftheblades are'properly shaped to fit 1nto these curved retaininggrooves. Theblades are secured against radial movement by theinterfitting serrations inthe side walls of the grooves and the roots,respectively.

I A particular object of my 1I1V6I1l31011 1 to provide means for bracingthe blades against each'other adjacent the root port ons, and thus toprovide a more rugged type of bladin'g construction; p Y A furtherobject is to provide means for locking the blades in their retaininggrooves against axial movement, that is, movement lengthwiseof thegroove;-

In accordance with my invention, the base portions of the respectiveblades are provided with buttress-like enlargements having arcuate sidewalls, the 'side'walls'of each enlargement being adapted to abut theside walls of the next adjacent enlargement in such a manner as to bracethe bladesagainst movement lengthwise of their" retaining grooves. Thesidewalls of the enlargements are so: formed that with one blade mountedin place,the next adjacent blade can beinserted .without interference.of the adj acent side grooves, this being preferably accomplished byforming the said adjacent side walls of the enlargements and the sidesof the root portion'of said next adjacentblade about "a com Theseenlargements thus serve anna amps the'dual purpose of strengthening theblades and of locking them in the rotor.

Theabove and other objects are effected by.

my invention, as will be apparent from the following description andclaims taken in.

connection with the accompanying drawings,

forming a part ofthis application, in which:

F 1g. 1 is a perspective view offa p'ortion'of a place Fig. 2 is asection on the line I'III of Fig. 1;and,

Fig. ,3 is a section on the line 111411 of Fig. 2. r In the drawing, Ishow a turbine rotor in the form of a disc, indicated generally, at 10in Fig. 1, and fitted with a number of blades 11 arranged 'ina row aboutthe periphery of the rotor. The blades ll are provided with rootportions 12, which are curved transversely, or in the direction of fluidflow, to conform in a general way to the curvature of the blades, andwhich are provided with serrations 13 adapted to interlockwithserrations it formed in the sidewalls of the transverse retaininggrooves 16. grooves are, of course, curved similarly to the rootportions. 'The serrations '13 and 14,

therefore, serve to restrain the blades from moving radiallyin'their'respective grooves.

In this type of construction, the curved root portion followsapproximately the curyature of'the' blade section so-that the blade isdirectly over its anchoring projection, or

root portion and hence,the bending stresses are greatly reducedand arelatively strong andcompact anchorage is provided. 7

In order to 'provide for bracing and strengthening such blades at theirbase portions and to provide for locking the respective blades againstmovement lengthwise of the respective retaining grooves, I have providedbuttress like enlargements 17 on the base portions of the respectiveblades, and these enlargements have arcuate side walls, the curvatureofwhich is similarto that of the retaining grooves. Each enlargement hasa concave side Wall 18 and a convex side wall 119-, the-concave sidewall'of each en- .largementbeing adapted to abutthe lVQK. M

rotor, showing some of the blades in.

These retaining.

side wall of the enlargement of the next ad-. jacent blade, and, due tothe curvature of" therespective side walls, to lock the blades againstaxial'movement. w a

This will be more apparent from a consideration of Fig, 2, wherein the,convex side wall19 of the enlargement 17,:is shown as an are describedabout the center 21 and haw ing a radius B. As shown] in this figure,the center 21 falls upon the line AB which is parallel to the side orthe rotor disc 10, and intermediate the axial extent of the enlargements. 7 For convenience, the 1n Flg. 2 have been designated as 17,17and 17 respectively. The convex sidewall 19 of the enlargements 17obviously must have the same curvatureas thejuxtapesed, concave sidewall 18 of the adjacentenlargement'lz", for otherwisefltwould not bepossible to slide the enlargement 17 past the enlargement 17 ininserting the blades into their respective. slots in the rotor. from thecenter 21, along the line AB. a 'distance equal to the maximum thicknessof the enlargement 17 is the center'22 about which the convex side wall19 of the enlargement 17 is formed as an are having the same radius R.Likewise, the concave side wall of the next enlargement 17 is formed ina similar manner with the same-radius about thesame center.

Considering theenlargement 17, it will'be seen that-as the op'positesidewalls of this enlargement are formed as arcs having the same radius ofcurvature,"but having difi'er ent centers, this enlargement must haveits ma-ximum thickness circumferentially of the rotor on the line AB asdesignated by the dimension L. Since, ifthe arc forming the convex sidewall. 19 of the enlargement 17 be completed to a circle, then thiscirclemust necessarily intersect a circle formed in the same manner byextending the concave side wall of the same enlargement Since'thesecircles intersect each other,'it follows that the adjacent arcs of thesecircles nust approach each other. Hence, these enlargements have agreater thickness in their. central portions than at the sides thereof,and the dimension L will always be greater than either the dimension M,or the dimension N, which indicate the respective thlcknesses of theenlargements at the end portions thereof. Furthermore, as the curvatureof the adjacent side walls of the respective enlargements is the same ineach case, it will beapparent that the blades may he slid into theirrespective grooves, one at a time, and that each blade will 'belocked-in place between the enlargements oft-he adjacent blades.-

As'will be observed from a consideration of the above, the curvature ofthe root portions ancllthe' grooves must be so related to curvature ofthe enlargement; asto. permit enlargements shown Spaced each blade to beinserted after one of the adjacent blades has been inserted withoutinterfering therewith. Apreferred manner of accomplishing this is toform the sides of the root portion and the groove and one sideofthe'enlargement of each blade about a common center; the other side ofthe enlargement being formed to contact with the enlargement adjacentthereto, that is, about the center of curvature of the adjacent rootportion and groove, which is spaced a distance equal tothe pitch oftheblades at the enlarged portions.

This-will be apparent from Fig. 2, wherein the dotted lines 24 and 25,are meant to indicate that the sides of the root portion and the grooveassociated with the-enlargement 17 are formed about the center 21, whichis the center-of curvature of the concave side wall 18 of-theenlargement 17. It will thus bejapparent that the blade having the en-..largement 17, maybe inserted atter the blade having the enlargement 17is in place, andsthat the concave side wall 18 of the former will slidealong the convex side wall 19 of the latter. V

Any suitable provision may be made for the ln's'ertion of the lastblade. For example,

if the blade 17" is the last to be inserted,

the convex side wall 19 thereof may be. relieved along a curved; surfacewhose center is the center 22,,as indicated by the line 26, to provide amaximum thickness equal to the dimension N. This permits the convex sideof the enlargement 17. to pass the corner 27 of the adjacent enlargementThe enlargement Y17'. and its associated root portion may then besecured against movement transversely ofthe rotor in any suitablemanner, as by caulking or pee'nin'g the root portion.

I From the above description, it will be seen that I haveprovidedinterlocking enlargements for blades of the character set forth,which look the blades in the grooves and which brace the blades againsteach other,

1. The combination of a rotordischa ving.

b1ade=holding grooves disposed transversely of its periphery, andbladshaifing :rootportions secured in the grooves and provided withenlargementsabuttin each other along curved surfaces;

my invention in but Q images 2. The combination of a rotor having a rowof curved blade-holding grooves, the grooves extending transversely ofthe row, and bladeshavingreurved rbot portions secured in the groovesand provided with enlargements abutting each other alongcurved 7surfaces.

3. In a turbine, the combination of a rotor, a row of blades, meansproviding forthe attachment and detachment of the blades by lateralmovement thereof relative to the rotor, and interfitting enlargementscarried by the blades, each enlargement having contact surfaces whichare convex and concave in a direction transverse of the rotor and theconvex and concave surfaces of each enlargement having spaced centers ofcurvature.

at. In a fluid motor, a rotor and arrow of blades mounted thereon, saidblades having root portions and enlarged portions intermediate theblades and the root portions, the opposite sidesof each enlarged portionbeing formed along arcuate surfaces whose centers are spaced,circumferentia-lly .of the rotor, a distance equal to the pitch of theblades at the enlarged portions, and said root portions being secured ingrooves in the rotor extending transversely of the row.

5. In a turbine, the combination of a rotorhaving curved grooves, eachgroove having concentric sides, and blades havin curved root portionsfitting the grooves an having abutments provided with contacting curvedsurfaces,-the root of each blade and one abutment surface of that bladeand the contacting abutment surface of the next adjacent blade being allconcentric.

6. The combination of a rotor having a row of blade-holding grooves, thegrooves extending transversely of the row, and blades having rootportions secured in the grooves and provided with abutting enlargements,the sides of the'root portion and grooves and one side of theenlargement of each blade being formed along arcuate surfaces having acommon center disposed intermediate the axial extent of the grooves.

7. In a fluid machine, a rotor having an annular row of blade-holdinggrooves extending transversely of the row, and blades having rootportions inserted in said grooves and abutting enlarged portlons, thesides of each groove and the root portionthere n being formed along arcshaving a common center, one side of an enlarged portion being formedalong an arcuate surface whose center coincides with said common centerof the associated root portion and the opposite side being formedconjugate to the adjacent side of the enlarged portion abuttingtherewith. I

8. In a fluid machine, a rotor having an annular row of blade-holdinggrooves ex tending transversely of the row, and blades having rootportions inserted in said grooves and abutting enlarged portions,jther'sides V of each groove and the root p'ort i'on' therein .beingsformed alOng arcs having a common center; disposed intermediate the Iaxial, ex'-.

tent of the-grooves, one side of an. enlarged "port-ion being formed'along an arcuate su'r facewhos'e center coincides with said commonlj.center off the associatedlroot portion and the opposite r-side'beingformed conjugate to the adjacent side of the enlargedporitionf abuttingtherewith; I I A 9. In a fluid machine, ga' rotor having an annular rowof 1 blade-holding grooves having concave and convex sides' andextending transversely of the row, I and blades having root portionsformed with concave and consides inse'rted'inthe grooves and havingabutting-enlarged portions, the-concave and convex sides of the groovesand root portions being formed to permit'ins'er'tion of the rootportions in the grooves laterally of the row from-one side thereof,meansextending laterally of the concave and convex-sides of the root'portion's for anchoringthesame in the grooves, one side of theenlargedportion of a blade and the adjacent or abutting side of the enlargedportionof the adjacent blade being formed to permit'insertion of theroot portion ofthe first blade while the second bladei's'in'place, and.the other side of the enlarged portion of the first blade being formedsimilarly to the first-mentioned side thereof but spaced therefrom adistance equal to the pitch of the blades 'at the enlarged Portions. V r

' 10; In a fluid machine, a rotor having-an annularrow of blade-holdinggrooves hav-' ing concave and convex sides and extending transverselyof't'he'royv, and blades havlng root portions formed with-.concaveandconvex sides inserted n the grooves and having 1 enlarged portionscontacting with each other -along contacting surfaces, the" concave and-"convex sides of the slots androot-portionsbeing formed to permitinsertion ofthe root portions in the grooves laterally of the row fromone side thereof, means extending laterally of the-concave and convexsides of the root portions for anchoring the same in the grooves, oneside of the enlarged portion of a blade and the adjacent or contactingside of the enlarged portion of the adjacent blade being formed topermitinsertion of the root portion of the first blade while the secondblade is in place, and the other side of the enlarged portion of thefirst blade being formed similarly to the first-mentioned side thereofbut spaced therefrom a distance equal to the pitch of the blades at theenlargedv r I i 3%183358 the; grooves, and. abutting enlarged portionsintermediate the blade; and root portions, saidi root and enlargedportions having curved; sides, one side of the enlarged por- 5 tion of ablade being-concentric with the corresponding side of the root portionof the bladeand the opposite side of the enlarged portion beingconjugate to the abutting side of the adjacent enlarged portion.

12. In a fluid machine, the combination of a rotor having an annular rowofblade-holding grooves, havingncurved sides and extending transverselyof the row, and blades having blade politions, root portions secured inv5 the grooves; and abutting enlarged portions intermediate the blade androot portions, "said root and enlarged portions having curvedsides,v oneside. of the enlarged portions and the corres ondingside of the root '20portion of a blade eing formed along arcs 7 having a common centerdisposed intermediate the axial extent of the grooves, and the oppositeside of the enlarged portion being conjugate to, the abutting side ofthe adjacent enlarged portion. a 13. In a fluid machine,la rotor havingan X annular row of "blade-holding grooves extending transversely of therow, and blades having root portions inserted in the grooves and havingabuttingenlarged portions, the

side Walls'of the groovesandthe-sides of the root portions being formedwith interengaging parts retaining the root portions in the grooves butpermitting insertion of the root .85 portions in the grooveslaterally'of the row from one side thereof; the sides of the grooves andthe root portions and the abutting surfaces of the enlarged portionsbeing so formed and arranged relatively to each other i 40 that Whenoneblade is in place, the root portion of a-next adjacent blade may beinserted andwhen inserted, the enlarged portion thereof contacts theenlarged portion of said one blade and locks the same against movementlateral-1y;v oiithe row.

In testimony whereof, I have hereunto subscribed iny name'this 27th dayofMay, 19.29.

BENJAMIN V. DEN-SMOKE.

